NSW farmers are optimistic that the sale of Australia's largest grain handler, GrainCorp, to the American agribusiness, Archer Daniels Midland, won't go ahead.

Delegates at the NSW Farmers Association conference in Sydney have voted unanimously to call on the Federal Treasurer, Chris Bowen, to block the $3.4 billion takeover bid.

Chair of the Association's grains committee, Mark Hoskinson, says the group has written to Mr Bowen.

"After everything that AWB went through, there was no charges or anything laid against any of those people and then the government decided to take away our marketing system, and now we have this ADM coming in who have a raft more issues facing them," he said.

"And it was overwhelming support that this is not the people we want to see controlling our east coast."

Shadow Agriculture Minister, John Cobb has thrown his support behind the push to stop the sale of GrainCorp to ADM.